This invention relates to a new process for making lubricating oil additives and to the products prepared by this process. It also relates to lubricating oil compositions containing the products of this invention.
The use of halogenated and sulfurized antioxidants and antiwear agents in lubricating oil additives has long been known; however, the additives known in the art have a variety of drawbacks. In some cases, antioxidant benefits have been sacrificed to achieve improved antiwear activity. In other cases, antiwear activity is sacrificed for antioxidant activity. When attempts have been made to prepare an additive having both antioxidant and antiwear activity, the corrosivity to metals, especially copper, has been high.
A variety of approaches have been tried in the past in the attempt to find a good antiwear-antioxidant additive having low metal corrosivity. U.S. Pat. No. 2,213,988 teaches halogenated thioethers which combine sulfur and halogen in a single molecule. Other additives combine a thioether antioxidant with a chlorinated wax.
Representative of other approaches are the following:
U.S. Pat. No. 2,514,625 describes chlorinating paraffin wax to about 15% to 25% chlorine content and then condensing with sodium monosulfide and sulfur or sodium polysulfide to produce an additive containing about 10% to 20% sulfur. In an example, a chlorinated paraffin wax containing 20% chlorine is reacted with sodium monosulfide and sulfur to yield a product containing 14% sulfur and 2.5% chlorine.
U.S. Pat. No. 2,744,070 describes reacting a non-conjugated olefinic C.sub.6 -C.sub.30 hydrocarbon with about a stoichiometric equivalent of a sulfur halide at 0.degree. to 50.degree. C. and then condensing with a water soluble inorganic higher polysulfide at 50.degree. to 100.degree. C.
U.S. Pat. No. 3,852,206 describes reacting a naphthenic base mineral oil with sulfuric acid and then treating the unneutralized oil with a sulfur halide to incorporate both sulfur and halogen into the oil. The additive is said to contain up to 18% by weight sulfur and up to 5% by weight total halide.
The additives manufactured by our new method are prepared in a simple and economical one-step process which produces additives having very good antioxidant and antiwear properties and very low corrosivity to metal surfaces.